Thanks to DVguru for pointing out a fascinating post at starwars.com that uses 151 still frames for a side-by-side comparison of the original 1980 version of The Empire Strikes Back and the remastered 2004 release. If you have any interest in the films, and digital effects and compositing in particular, then it is worth a step through them all. There are captions at the bottom to describe what they have done.
For those that may not know, Lucasfilms recently released double dvd versions of all of the “first” 3 Star Wars films with both the unaltered original films one one disc as well as the remastered 2004 versions of the film on another disc. Get them soon as they are being marketed as limited edition!